Automatic door operator



Aug. 14, 1956 A. WIKKERINK 2,758,835

' AUTOMATIC DooR oPERATOR v FiledAJuly 31, 1952 s sheets-sheet 1 IN V ENTOR.

OMMr-M Aug. 14, 1956 A. WIKKERINK 2,758,835

AUTOMATIC DOOR OPERATOR Filed July 51, 1952 s sheets-shew 2- 1N V N TOR.

A TTQE/VEYS Aug 14, 1956 1 A. WIKKERINK 2,758,835

AUTOMATIC DOOR OPERATOR Filed July 31, 1952 3 Sheets-Shea?l 3 AM/CE H.W/KKEe/N/c MLLM+MJA AUTOMATIC 'DOOR OPERATOR' Lance A. Wikkerink,Milwaukee, Wis., assigner, by mesne assignments, to Treadway Corp.,Woodbridge, N. l., a corporation of New Jersey Application .luly 3'1,1952, Serial No. 361,871

Ll?) Claims. (Cl. 268-34) This invention relates to an automatic dooroperator.

It is the object of the invention to provide an automatic door operatorwhich exerts its greatest force on the door in the initial stages ofdoor movement whereby to overcome the inertia of the door. Conversely,the force of the operator on the door at the end of door movement isreduced in the device of the present invention whereby to avoid slammingthe door and conserve energy otherwise thus wasted. Accordingly, in thedevice of the present invention, the thrust of the door operator isdirectly related to the resistance of the door and is materially reducedat the end of door movement.

in the `device of this invention, differential door operator thrust isdeveloped by progressively changing mechanical advantage of atransmission mechanism between a motor or motors (which may haverelatively constant thrust) and a connection to the door. Because nochange in thrust is required of the motor, a motor of relatively smallcapacity is all that is required to power the device of this invention.The relatively great inechanical advantage in the transmission mechanismat the beginning of motor operation more than makes up for the smallsize of the motor. This is in sharp contrast to prior art devices whichdo not take into account changes in door resistance. In such prior artdevices the motor is made large enough to overcome maximum resistance ofthe door. After the initial inertia of the door is overcome the excessenergy of the motor is wasted in slamming the door against its frame.Here, however, my novel transmission compensates for changes in doorresistance and utilizes the full capacity of the motor throughout therange of door movement. As compressed air is commonly used to actuate acompressed air motor in devices of this type, my operator only requiresan air compressor of materially smaller size than those of the priorart.

Another object of the invention is to provide a novel uid control valvefor the fluid motors iny the door operator of this invention. Thiscontrol valve provides for a time lag or dwell between door opening anddoor closing movements for purposes hereinafter explained.

I also provide a novel electric actuating circuit for my door operator.The circuit is provided with an interlock which locks the control valvein one position when the safety mat switch is closed before the approachmat switch is initially closed, thereby holding the door closed untilthe safety mat switch is opened.

The door operator consists of a shaft having motion transmittingconnections to the door and a crank on the shaft, a powered actuator andmeans for guiding the actuator against the crank arm on a path which iseccentric with respect to the axis of rotation on the shaft. In thecourse of its eccentric path the point of contact of the actuator withthe crank shifts along the crank to vary the moment arm of the crank.Moreover, in the initial movement of the actuator, the crank is ininclined position with respect to the path of movement of the actuator.Accordingly, in the initial movement of the actunited States Patentfs"le ator, the actuator acts against the crank in the manner of a wedgeto increase the mechanical advantage of the actuator respecting theshaft. This combination of wedging action and shifting of the point ofcontact of the actuator with the crank increases the torque exerted onthe shaft during the initial movement of the actuator. Near the end ofits stroke the point of contact of the actuator with the crank has movedclose to the axis of shaft rotation with corresponding reduction inmechanical advantage and torque.

Other objects and advantage of the invention will be more apparent toone skilled in the art upon examination of the following disclosure.

In the drawings:

Fig. l is a fragmentary View in perspective of a building wall showing adoor and door operating mechanism according to the present invention.

Pig. 2 is a horizontal cross section through the door operator of thepresent invention.

Fig. 3 is a cross section through a fluid control valve according to thepresent invention. 'v

Fig. 4 is a cross sectional view taken along the lines lfll of Fig. 3.

Fig. 5 is a cross sectional View taken along the lines 5 5 of Fig. 4.

Fig. 6 is a cross sectional View taken along the lines 6--6 of Fig. 2.

Fig. 7 is a schematic circuit diagram of the electric circuit whichcontrols the door operator according to the present invention.

Fig. 8 is a graph plot of shaft torque against door position.

The invention has particular utility in super markets and other publicbuildings where it is inconvenient for pedestrians to manuallymanipulate entry and exit doors. l have chosen to describe the presentinvention in an embodiment in which the weight of the pedestrian im.-posed on approach and safety mat switches actuates an electric controlcircuit for the door operator which opens and closes the doorautomatically depending on the position of the pedestrian respecting theswitches. The invention does not reside in the specific mat switchesdisclosed, however, as electric eye devices etc. could be substitutedwithin the scope of the invention. While mechanisms of the general typedescribed are in use today the present invention constitutes animprovement thereover in the respects herein mentioned. I

Fig. l shows in fragmentary perspective a wall 10 provided with a doorframe 1l and a door 12 hinged at 13 to the frame. The door opens in thedirection of traic. The entrance side of the door is provided with a oorapproach mat i4 and the exit side of the door is provided with a safetymat l5. A pressure approach switch 16 and a pressure safety switch i7are concealed beneath the respective mats to be actuated by the weightof a person walking on the mat.

The upper rail 20 of the door is provided with a bracket 2i, a link 22.and an operating arm 23 pivoted to the end of link Z2 by pin 2d. Theother end of arm 23 is adjustably fixed to the downwardly projecting endof a rock shaft 25 rotatably mounted in the casing which houses theopening mechanism. The shaft 25 and arm 23 are provided withcomplementary mating tapers 18 (Fig. 6) permitting adjustment in theirfixed connection. Bolt 19, seating against washer 29, draws the taperedsurfaces into frictional locking engagement.

The casing Sil in which shaft 25 is mounted has both inner and outerwalls. Heavy metal inner walls 26, 27, and 28 (see Fig. 2) enclose achamber of generally trapezoidal configuration containing thetransmission mechanism and support the entire structure from the doorframe il.. A light metal shell 3l forms with walls 26, 27

and`28 an outer chamber containing the fluid motors and control valveand conceals all operating mechanism.

Swinging movement of the lever arm 23 on the axis of rotation of shaft25 is effective through the link 22 and bracket 2l to open and close thedoor. Within the casing the shaft 25 is provided with a crank 32 havinginclined or wedging surfaces 33 and 3ft. Shaft 25, together with arm 23and crank 32, comprises a bell crank.

The walls 26 and 27 of the casing 3@ are in oblique connection with theend wall 2S and converge toward said end wall for reasons hereinafterappearing. Walls 26 and 27 are .provided with openings 35 and 36respectively through which operator or piston rods 37 and 33respectively of pistons 41 and i2 project into the interior of thetrapezoidal casing to exert thrust on the opposed inclined surfaces 33and 34 respectively of crank 32. Pistons 41 and 42 are mounted in motorcylinders 43 and 44 which have their inner ends seated in the openingsand 36 and their outer ends supported on the bracing rods 45 threadedinto the walls 26 and 27 of the casing, as illustrated at 40 in Figs. 2and 6. Rods 45 carry head caps 46 in which seat the outer ends ofcylinders 43 and 44.

As so positioned the cylinders are substantially at right angles to theWalls 26 and 27 of the casing. However, as the walls 26 and 27 areangularly related, the cylinders are also. The cylinder head caps 46 arethus disposed near the outer corners of casing 3l and fluid connections47, 48 extend beyond the plane of wall 2S and are laterally aligned foreasy connection to the valve 62 mounted on casing wall 28 therebetween.

Cylinders 43 and d4 are supplied through fluid connections 47 and 43with pressurized fluid, usually air, to constitute the cylinder 43 and44 fluid motors which drive the pistons 41, 42 into thrust engagementwith crank 32.

The inner ends of the piston rods 37 and 38 are pinned respectively atSi and S2 to guide links 53 and 54 provided with pivots and 56 tixed tooor 57 of the casing. The pivotally connected ends of the piston rods 37and 38 and links 53 and 5drespectively are provided with antifrictionrollers 53 and S9 which contact the inclined surfaces 33 and 34 of crank32.

Fixed pivots 55 and S6 of links 53 and 54 are oiset from the axis ofoscillation of the shaft 25. Accordingly, the paths of movement ofrollers 53 and 59 under the thrust of pistons 4l and d2 will constitutearcs which are eccentric with respect to the axis of rotation of shaft25. The pistons il and 42 are slightly tiltable in their cylinders toaccommodate such movement. Thus the elfective moment arm of crank 32changes throughout the stroke of the pistons. in the completelyretracted position of the piston (shown at the right in Fig. 2), roller53 bears at the extreme end of the inclined surface 33 of crank 32. Inthe extreme forward position of the piston (shown at the left in Fig.2), rolier 53 bears against inclined surface 34 of crank 32 near thebase of the crank and relatively near the axis of rotation of shaft 25.Accordingly, in the initial movement of the pistons, the moment arm ofcrank 32 is greater than towards the end of piston movement.Consequently greater mechanical advantage and torque is imposed on theshaft in the initial movements of the piston.

Moreover, in the initial movement of the piston, the rollers 56 and 59act on the inclined surfaces 33 and 34 of the crank 32 in the manner ofa Wedge whereby further mechanical advantage occurs in the initialdriving movements of the pistons. Thus there is a complex actioncombining a wedging action and a change in moment arm resulting ingreater mechanical advantage at the beginning of piston stroke than atthe end. Accordingly, the torque on shaft 2S is greatest when the dooris started from a position of rest. Conversely, at the end of pistonstroke, the torque is greatly reduced thereby eliminating slamming ofthe door against the frame. As before noted all the energy of the motoris used for useful work and none is wasted. A graph in which shafttorque is plotted against door position is shown in Fig. 8 of thedrawings. This graph clearly shows how torque is directly related to theinertia resistance of the door.

The plot in Fig, 8 is taken from actual measurements using a springscale at the end of lever arm 23. In the test aforesaid the lever armwas 27 inches in length. The uid motor was under a constant pressure of70 pounds per square inch. Measurements were taken of thrust at the endo-f `the lever at various degrees of door opening movement. As alsoindicated on the graph the following chart shows the relation betweenshaft torque and door position:

Shaft; torque in pounds Door position in dcat end of 27 inch lever grecsof door opening arm movement Because of this novel distribution oftorque during the course of piston movement a much smaller aircompressor than has heretofore been required is needed to power thedevice of the present invention. Heretofore, in prior art devices whereincreased mechanical advantage was not employed at the beginning of dooropening movement, greater thrust had to be used to start the door. Asthe piston is part of a constant thrust motor, this excessive thrust wascontinuous throughout vthe range of door movemeut yonly -to be absorbedat the end ol` the stroke is ineffectively banging the door `against theframe. ln the present invention great mechanical advantage is employedto start the door. A correspondingly smaller air compressor isaccordingly needed.

The bell cranks 23, 25, 32 and links 53, 542- vmay be regarded as atransmission mechanism between the iluid motors `and the door. Becausethe transmission mechanism is adapted to change mechanical advantagebetween the motor and the door a constant thrust motor can be used withall the advantage of a variable thrust motor.

Fluid motors 43 and 4,4 are supplied with fluid, preferably compressedair, 'through a liuid control valve mechanisni indicated generally as62. As best shown in Fig. 3, valve 62 comprises a cylinder 63 in whichpiston 64 is slidable. Piston 64 is hollowcd at b5 to receive acompression coil spring 66 which seats against the end wall of cylinder62 to bias the piston toward the leit in Fig. 3. The hollowed socket andinterior of the cylinder 63 together comprise a liuid chamber 67 whichvaries in capacity depending on the ,position of the piston. The portionof the piston-64` beyond the spring 6b moves in fluid chamber 70enclosed by the valve casing 62. Charnber 7i) is in constantcommunication with a source of compressed air through fluid pressureconnection 7i and flexible line 72. Chamber 79 is closed by asubstantially planiform cover member 73 connected by bolts 74 to thevalve casing 62. Cover member 73 is provided with three uid ports 75,76, and 77, aligned in the direction `of piston movement, to coact witha valve block 78 mounted on the piston 64. Valve block 7S comprises abearing face provided with an annular groove or air channel 79 ofdiameter sufficient to simultaneously span and connect the center port77 with one or the other of ports 75, 76. In Fig. 3, port 76 is exposedto the compressed air in chamber 7@ and valve ports 75 and "i7 are incommunication through the annular groove 79 in the valve block.

Valve block 78 comprises a body portion 30 seated in a complementaryvlateral socket 83 in piston 64. Body portion Si) is socketed at Si toreceive compression coil spring '82 which is biased against the end ofsocket 83 to insure good sealing contact of the valve block 78 about theports 7S, 76 and 77.

vFor the purpose of this description, port 76 inay be regarded asconnected through coupling 34 and fluid line 85 to coupling 47 (Fig. 2)which serves fluid motor 43. Port 75 is connected by means of thecoupling 86 and fluid line 87 to coupling 48 which serves fluid motor44. Port 77 communicates with the atmosphere through needle valve 88.The connections shown operate the door in the organization shown in Fig.l and in which the door operator mechanism is mounted on the same sideof the frame as the door is hinged. Floor mat 14 is at the approach sideof the door and floor mat 15 constitutes the safety imat. lf doorswinging movement were to be reversed in Fig. l it would be simplynecessary to reverse the connections of fluid lines 85 and S7 tocouplings 47 and 48. In that case, of course, mat 15 would be theapproach mat and mat 14 would be the safety mat. The control valvemechanism 62 is so mounted on wall 28 of the casing that reversal ofthese connections is accomplished simply by rotating the control valve62 through 180 and making the indicated connections. For this puiposecouplings 86 and 84 are equally laterally spaced from the means on whichthe valve 62 is mounted to casing wall 28.

In the position of the valve shown in Fig. 3, line 85 is under fluidpressure to actuate fluid motor 43 and connect cylinder 44 to theatmosphere. Motor 43 thus holds the door closed as in Fig. l. This isthe normal position of the operator with both approach and safety matswitches open. Chamber 67 of the control valve, however, i-s providedwith a pressure release line 91 cnntrolled by a rubber or other elasticvalve pad 92 normally closed against the end of the tube 91. ln thiscondition air pressures in control valve chambers 70 and 67 are equalbecause of a bypass between said chambers resultant from the relativelyloose fit of the piston 64 in cylinder 63. The piston is then freelybiased to the left by spring 66. Valve 92, however, is mounted on thearmature 93 of solenoid 94. Armature 93 is pivoted on pin 96 to bracket95 and has a rearward extension 97 under tension of spring 100 anchoredon ear 101 to bias the valve pad 92 against the end of tube 91.

When solenoid 94 is electrically energized, it attracts the armature 93from the position shown in Fig. 3 to the position shown in Fig. 2 toopen valve 92 and release the compressed air in chamber 67. Thereupon,pressure of the compressed air in chamber 70 will force the piston 64 tothe right as shown in Fig. 3 against the bias of spring 66, said biasbeing insuflicient to resist the air pressure in chamber 70. Piston 64will move until its end 63 strikes cylinder shoulder 69 which iixes theextreme right hand position of the piston. Movement of the piston 64 tothe right, of course, alters the position of valve block 70 and servesto connect port 76 to the release port 77 to inactivate and exhaust airpressure in fluid motor 43 and to connect port 75 through chamber 70with the source of air pressure to energize motor 44. Motor 44 thenopens the door through the transmission mechanism in the mannerhereinbefore described.

Because safety switch 17 and approach switch 16 are connected inparallel, as hereinafter more fully explained, the person walkingthrough the door from the approach mat to the safety niat will maintainthe solenoid 94 energized until he steps oif of safety mat 15. Bothswitches 16 and 17 are thereby opened to cle-energize solenoid 94.Spring 160 then returns valve 92 to closed position whereupon compressedair leaking from chamber 70 to chamber 67 through the bypass aforesaidwill gradually equalize pressure in said chambers and permit spring 66to return piston 64 toits Fig. 3 position.

The strength of the spring 66 and fluid capacity of the bypass or airbleed between chambers 70 and 67 establishes a time lag or dwell betweenclosure `of valve 92 and return of piston 64 to the position in whichline S5 is again under pressure to energize motor 43 for return of thedoor to closed position. This dwell is highly important in my device forsafety reasons. By setting a definite time lag between release of switch17 and activation of door closing motor 43, a person passing through thedoor is well away from the safety mat before the door closes. Aconstruction in which air bleed can occur because of the loose lit ofpiston 64 in cylinder 63, is less expensive than provision of a separateand distinct bypass channel of limited capacity between chambers 67 and70.

The electric circuit for controlling the operation of control valve 62through solenoid 94 will now be described. This circuit is shownschematically in Fig. 7. A 24 volt transformer 102 is preferred toenergize the solenoid. Other power sources, of course, could be adaptedfor use with the disclosed circuit. The transformer receives current atvolts through input lines 103 and 104, and supplies current at 24 voltsthrough its output lines 105 and 106. Terminal 107 of the solenoid 94 isdirectly connected to output line 105 of the transformer and the otherterminal 108 of solenoid 94 is connected through line 111 along twopaths of current liow as hereinafter indicated. Common line 111 branchesat 112 through approach mat switch 16, line 113 and output line 106 tocomplete one circuit with the transformer. Closure of switch 16 willnormally energize the solenoid.

Line 111 has a second branch at 114 connected through safety mat switch17, line 115 and single pole double throw switch 116. In its left handposition in Fig. 7 switch 116 completes the solenoid circuit throughline 117 to output line 106. Thus, with switch 116 in left handposition, switches 16 and 17 are connected in parallel and switches 17and 116 in series. Accordingly, even though switch 16 is open, if bothswitches 17 and 116 are closed, solenoid 94 will be energized. If,however, switch 116 is in its right hand position in Fig. 7, and safetymat switch 17 is closed, solenoid 94 is short circuited through seriesconnected switches 17 and 116. In that condition closure of approach matswitch 16 is ineffective to energize the solenoid because of the shortcircuit aforesaid.

Switch 116 dcsirably comprises a microswitch as illustrated in Fig. 2.Switch 116 is provided with an operator button 120 actuated by lever arm121 having a roller 122 mounted in the path of cam surface 123 on shaft2S. Accordingly, switch 116 is automatically thrown from one position tothe other on rotation of shaft 25. In the position of the piston shaftin Fig. 2, in which the door is open, the solenoid 94 is energized. Thusswitch 116 is in its left hand position as shown in Fig. 7 so that aslong as either switch 16 or switch 17 is closed solenoid 94 will beenergized to hold the door open. When the door is in its closedposition, however, cam 123 will have caused switch 116 to move to itsright hand position shown in Fig. 7. As long as switch 17 is open,closure of switch 16 is effective to energize solenoid 94. As beforeexplained, when solenoid 94 is energized, control valve 62 is actuatedto energize lluid motor 44 to open the door. in the course of dooropening movement cam roller 122 on microswitch lever 121 will beactuated to change the position of the switch 116 from its right hand toits left hand position as shown in Fig. 7, so that when the pedestriansteps from the approach switch to the safety switch, the closure ofsafety switch 17 maintains piston 44 energized to hold the door open.

Assume, however, that someone is standing on the safety mat when thedoor is closed, switch 17 is closed and switch 116 is in its right handposition. Solenoid 94 is thus short circuited. Now if someone closesswitch 16 by stepping on the approach mat, current supplied by thetransformer 102 is short circuited around the solenoid through seriesconnected switches 17 and 116 and the door cannot change position. Thusthe person standing on the safety mat is protected from door openingmovement. As soon as the person on the safety mat switch steps aside,however, switch 17 opens to break the series connection around solenoid94 and the door will open in normal sequence. Solenoid 94 would also beshort circuited if during the eXtreme initial movement of the door fromclosed toward open position switch 17 is closed. Cam face 123 is sodimensioned that switch 116 is held in right hand position (Fig. 7)until the door has made substantial pro-gress in its opening movement.Thus one stepping on safety mat 1S after the door has just started toopen is protected.

While both door opening and door closing movement is normally controlledat relatively fixed accelerating and decelerating rates depending uponthe rate of fiuid feed through lines 85 and 87 to the respectivecylinders' 43 and 44 and the structure of the transmission mechanism, itis conceivable that in either door opening or closing movement a gust ofwind or other force might seize the door and increase its speed in thedirection of movement of the energized piston and bang the door againstthe frame or otherwise damage it. rlhis would be possible unlessotherwise provided against because as so far described the onlyresistance offered to door movement is door inertia and the resistanceof the inactive fluid motor. The rate of fluid exhaustion from theinactive motor is controlled only by needle valve 88 (see Fig. 3). Thisis normally set to exhaust at a relatively rapid rate so as not tointerfere with the operation of the active motor. Normally the inactivemotor does not provide sufficient damping if a sudden gust of wind wereto seize the door.

To provide against this contingency, a snubbing cylinder 124 is mountedby means of its threaded nipple portion 125 in a suitable tappedaperture in wall 26 of the casing (see Fig. 2). Cylinder 124 is filledbetween movable pistons 126 and 143 with hydraulic fluid. The free end133 of outermost piston 126 is provided with a generally concave socket122 to receive plunger arm 127 which is pinned at 12S to second crank129 on shaft 25.

The space between movable pistons 126 and 143 isl divided into opposedchambers 134 and 135 by valve seat member 136 seated against snap ring137. Valve seat member 136 is provided with a bypass channel 140 ofsmall capacity and with a central valve opening 141 of larger capacity.Check ball 142 alternately releases and closes valve opening 141depending upon the direction of ow of hydraulic fluid (desirably oil)against the valve seat 137 as is well known in the art. Piston 143 isprovided with a rearwardly open socket 144 in which is seated acompression spring 145 which bears against snap ring 146. Spring 145normally biases piston 143 toward the valve seat member 136 to flow oilthrough both the bypass 140 and the main valve opening 141 to forcemovable pislton 126 toward plunger 127 and require the piston to followthe plunger in all withdrawal movement thereof.

During movement of plunger 127 against piston 126 check ball 142 closespassage 141 and the oil must ow through bypass 140 toward piston 143 andagainst the bias of spring 145. Bypass 140 is sufficiently large so thatpiston 126 does not offer material resistance to plunger 127 undernormal conditions. Door movement is thus normally controlled solely bythe iiuid motors 43 and 44. However, if the door is seized by a gust ofwind, out of control of the motors 43 and 44, bypass 14@ is sufficientlysmall to meter oil flow therethrough and piston 126 will snub inwardmovement of the plunger 127 and in turn check the door. Both pistons 126and 143 are provided with suitable O-ring seals 130, and 131respectively to prevent escape of hydraulic fluid from confinementbetween the pistons. The angle of connection of crank 129 to shaft 25 issuch that plunger 127 tends to withdraw from its concave seat duringinitial movement of themotors 43, 44, but bears against its seat duringthe latter part of such movement.

From the foregoing description taken in connection with the accompanyingdrawings, it is clear that I have provided a novel door operator inwhich the torque imposed on the shaft operating the door variesthroughout the range of door movement to apply greatest torque in theinitial movement of the door where inertia is to be overcome and reducedtorque at the end of door movement. My novel fluid control valveprovides for time lag or dwell after the pedestrian has stepped off thesafety mat before the door closes. My novel electrical circuit providesfor complete electrical control of the solenoid and includes novelcircuit elements whereby closure of the safety mat switch before andduring initial movement of the shaft 25 will short circuit the operatingsolenoid to preclude opening of the door. My novel snubber is effectiveonly under abnormal circumstances and operates to check the door whenthe door is forceably removed from the control of the motors. My novelassembly of operator components provides for positioning the valve 62physicaily between the air connections to 'the pistons. The couplings 8i and 86 are symmetrical with respect to the mounting of valve 62.Accordingly, rotation of the valve through l is all that is required tochange air connections where the operator is converted from use on an inopening door to use with an out opening door.

I claim:

l. An automatic door operating system comprising a door operator havingfluid operated means for acting on the operator in at least onedirection of door movement, a fluid circuit including a connection tosaid fiuid operated means and a uid control valve in said circuit, saidcontrol valve having electric control means, an electric circuit forsaid electric control means, said circuit including an approach switchat the approach side of the door, a safety switch at the opposite sideof the door, a multiple position switch actuated in response to dooroperator movements and a source of electric current, said electriccontrol means having one terminal directly connected to said source andanother terminal connected to said source in series through said safetyswitch and said door operated switch in one position of the dooroperated switch, said door operated switch having another position inwhich both terminals of said electric control means are connectedthrough said safety switch.

2. The device of claim l in which said door operated switch is normallyin said another position when the door is ciosed whereby closure of thesafety switch will short circuit the electric control means and renderclosure of the approach switch ineffective to actuate the electriccontrol means, said door operating switch being actuated to said oneposition in door opening movement to place said safety switch inparallel with said approach switch.

3. The device of claim 2 in which said door operator comprises a shafthaving a cam surface, said door operated switch being mounted proximatesaid shaft and being provided with a switch actuating lever projectinginto the path of movement of the shaft cam whereby said switch isactuated from said another position to said one position on rotation ofthe shaft in a door opening direction.

4. The device of claim 2 in which said fluid control valve comprises acylinder and a piston within the cylinder and dividing the cylinder intoopposed chambers, fluid ports in one of said chambers, resilient meansbiasing said piston toward said one chamber and a fluid releaseconnection in the other of said chambers, said piston being providedwith a port covering member alternately covering and opening said portsin the movement of the piston from one chamber to the other, a controlvalve for said fluid release connection, huid bypass means between saidchambers, whereby to permit equalization of fluid pressure in saidchambers when said fluid release connection is closed by said controlvalve, said bypass means having fiuid carrying capacity less than thatnecessary to permit normal action of said resilient means whereby saidresilient means will move the piston toward the said one chamber at arate dictated by fluid bleed through the bypass.

5. An electric circuit for an operator having electrical actuatingmeans, said actuating means being provided with terminals, a source ofcurrent having a connection to one of said terminals, another of saidterminals being connected to said source through a plurality of switchesin series connection whereby all said switches must be closed tocomplete the circuit through said switches, and another switch inparallel with said series switches, one of said series switchescomprising a multiple position switch having one position completing thecircuit to said source and another position to short circuit the controlthrough the other said series switch.

6. An automatic door operator comprising a casing and a shaft projectingthrough the casing and having a lever arm for connection with a door, acrank on the shaft within the casing and a pair of fluid motors mountedat the exterior of the casing and having pistons and piston rods forwhich the casing wall is apertured whereby said piston rods extend intoproximity to the crank, swing arm guide means pivoted to the pistonrods, said swing arms having fixed pivots Within the casing offset fromthe axis of shaft rotation whereby said piston rods have arcuate pathsof movement eccentric respecting the axis of rotation of the shaft, saidpiston rods having means bearing at opposite sides of the crank wherebyto actuate the crank in both directions of shaft oscillation.

7. The device of claim 6 in which said shaft is provided with a secondcrank and a plunger pivotally mounted on said second crank, and a fluiddamping cylinder mounted on said casing and having means of connectionwith said plunger, said fluid motors having fluid pressure connectionsincluding a valve by means of which said motors are alternatelypressurized and exhausted to operate the door, said uid damping meanshaving a rate of movement greater than the rate of fluid motor operationwhereby to be normally inactive but to control door movement if saidshaft is rotated at a rate in excess of that normally produced by motoraction.

8. The device of claim 6 in which said casing comprises opposite wallsobliquely related whereby said uid motors are inversely obliquelyrelated, and control means mounted on a wall between said motors andwithin the included angle of said motors, said control means having uidconnections to said motors.

9. The device of claim 8 in which said control means is provided withmeans mounting it on said wall and terminals for said fluid connectionswhich are symmetrically disposed respecting said mounting means wherebythe connections of said fluid connections to said terminals can bereversed by rotating the control valve through 180 on said mountingmeans.

10. In a door operating device of the character described, asubstantially constant thrust fluid motor, motion transmitting doorconnections, and a transmission mechanism between said door connectionsand said motor, said transmission mechanism comprising means forconnecting said motor to said door connections with great mechanicaladvantage in the initial movement of the motor and progressivelydecreasing mechanical advantage thereafter, said transmission mechanismcomprises a 10 shaft having a lever arm, a crank on said shaft, a swingarm having a fixed pivot offset from the shaft, said motor comprising areciprocating member pivoted to said swing arm and in bearing contactwith said crank whereby the path of movement of said member as guided bysaid swing arm comprises an arc eccentric with respect to the shaft.

11. An automatic door operator for the powered movement of a door andfor imposing greater thrust on said door at the beginning of itsmovement than at the end of its movement, said operator comprising ashaft, motion transmitting connections from the shaft to the door, acrank arm mounted on the shaft, ya power operator movable against saidcrank arm to turn said shaft, and a link having a iixed pivot olset fromthe axis of shaft rotation and having a pivoted connection lto saidoperator whereby the path of operator movement comprises an arc aboutsaid link pivot which is eccentric with respect to the axis of shaftrotation whereby to shift the point of contact of the operator alongsaid crank arm and vary the moment arm of said operator with respect tosaid shaft depending on the position of the door.

12. The device of claim l1 provided with a second power operator mountedat the opposite side of said crank arm from said power operator andhaving a pivotal connection with a second link having a xed pivot oifsetfrom the axis of shaft rotation and at the side thereof opposite thefixed pivot of the Erst link, said second power operator having a pathof movement which comprises an arc eccentric with the axis of shaftrotation whereby said door is powered in both its opening and closingmovement and the moment arm of both said power operators is varied withrespect to the position of the door.

13. The device of claim 11 wherein said crank arm comprises a wedgesurface disposed at an oblique angle to the path of the rst incrementsof power operator movement whereby to increase the mechanical advantageof the power operator with respect to the shaft in said rst incrementsof power operator movement.

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